The 3rd Generation Partnership Project 2 (3GPP2) is a collaboration between telecommunications associations to make a globally applicable third generation (3G) mobile phone system specification within the scope of the International Telecommunication Union's (ITU's) IMT-2000 project. In practice, 3GPP2 is the standardization group for CDMA2000, which is the set of 3G standards based on earlier 2G CDMA technology.
In considering loosely backward compatible mode (LBC) in the 3GPP2 standardization process, the forward link (FL) of an orthogonal frequency division multiplex (OFDM)-based framework was proposed to include an FL superframe consisting of a superframe preamble followed by a certain number of Physical Layer (PHY) frames. FIG. 1 is a diagram illustrating graphical examples of FL superframe 102 and reverse link (RL) superframe 103. FL superframe 102, provided from access network (AN) 100 to AT 101, includes superframe preamble 104 and several subsequent PHY frames 105-107.
FIG. 2 is a diagram illustrating a graphical representation of FL superframe preamble 104. FL superframe preamble 104, as shown, typically consists of eight OFDM symbols, symbols 200-207, for fast fourier transform (FFT) sizes of 512 and above. The first five OFDM symbols, symbols 200-204, in FL superframe preamble 104 are generally used to carry the two physical broadcast channels, namely the forward-primary broadcast control channel (F-PBCCH) and the forward-secondary broadcast control channel (F-SBCCH). An F-PBCCH packet is typically encoded over 16 superframes, and usually occupies ¼ of an OFDM symbol in each superframe preamble. An F-SBCCH packet is typically encoded over a single superframe and usually occupies four ¾ OFDM symbols in each superframe preamble.
The F-PBCCH typically carries system information (e.g., Rev number, CP length, Time and the like), which usually stays the same throughout the entire deployment region. The F-SBCCH channel is typically used to broadcast quick page (QP) messages in even superframes and to broadcast sufficient information, such as the information on the hopping patterns, the pilot structure, the control channel structure, and the configuration of the transmit antennas, to enable the mobile station to demodulate the traffic frames, in odd superframes. Also, the F-SBCCH channel usually contains some fields that have a tendency to change quickly, such as interference level (IoT) on the reverse-data channel (R-DCH) and LoadControl (2 bits for allowed access class).
As various access terminals (ATs), mobile devices, or the like travel through different sectors defined by various access networks (ANs), a base station of the AN does not typically know where ATs are within the sector during AT idle time. In order to maintain proper management of the AN sector, paging is used to keep track of idle ATs within the sector. Paging is the process by which the AN initiates a connection with an idle AT, such that the AT wakes to listen to the FL traffic. The AT does this wake-and-listen only at certain negotiated time intervals in order to conserve local AT resources. A page is typically transmitted to ATs using QuickPage messages on the F-SBCCH and/or Page messages on the Forward Traffic Channel (FTC).
The quick paging channel is usually transmitted every even superframe on F-SBCCH. In OFDM networks, the quick page may be transmitted in single frequency network (SFN) mode by sectors belonging to the same quick paging group. It is usually accompanied by SFN transmission of broadband pilots to provide better forward-quick page channel (F-QPCH) performance at the cell edges in order to help reduce interference in interference limited scenarios. This scheme generally gets full diversity advantage in both slow and fast fading.
Regular pages are usually carried on the forward-data channel (F-DCH), and can be sent in an SFN mode. This regular page message transmission channel is typically scheduled by a forward link assignment message (FLAM) in a shared control channel (SCCH), which is usually scrambled by a broadcast media access control identification (MAC ID) that is commonly known to all the ATs. The FLAM typically indicates the channel resource ID, modulation and coding scheme (MCS), and duration of the page message.
Each sector in the access network also broadcasts various overhead messages periodically to advertise the system parameters to all the ATs. For example, the ExtendedChannelInfo block is one type of overhead message defined in the Overhead Message Protocol in 3GPP2 air interface standards. These overhead messages are usually carried on a logical broadcast channel which is carried on the physical F-DCH in the traffic frames, PHY frames 105-107 (FIG. 1). This logical broadcast channel is differentiated from the regular traffic channel by being scheduled by a FLAM in the SCCH that is scrambled by a broadcast MAC ID commonly known to all the ATs. This logical broadcast channel is referred to as a broadcast channel in the following sections to differentiate it from the two physical broadcast channels, namely F-PBCCH and F-SBCCH, in the preamble 104 as described above. Typically, each sector broadcasts its overhead messages independently. Therefore, it is not necessary that this logical broadcast channel be transmitted in SFN fashion.
As noted above, paging channels are employed in wireless networks to page a subscriber station or AT, such as a cellular phone, in order to instruct the subscriber station to connect to the network for service. In conventional systems, the network has only a rough knowledge of a location of a subscriber station, and no knowledge of channel quality in the area of the subscriber station prior to page transmission. Consequently, a page message is typically sent over a wide region (e.g., a plurality of sectors) at low spectral efficiency due to such inadequate information. Thus, typical paging systems employ a paging channel that is transmitted independently from each sector in a paging region, which can be established based on a registration history for the AT. A page can then be transmitted to the AT by sending the paging message from each sector in the region. While such a paging message can be transmitted at approximately the same time, page transmissions from different sectors are typically independent of each other.
One method that has been developed to address this problem is discussed in U.S. Patent Publication No. 2006/0199596 A1, filed Jul. 5, 2005, entitled, “MULTI-SECTOR BROADCAST PAGING CHANNEL.” In this method, paging signal strength is improved at or near sector perimeters in a wireless network region by transmitting identical paging waveforms simultaneously from all sectors in the region and permitting over-the-air signal aggregation to combine signal energy near sector perimeters. Waveforms are modulated using an OFDM technique and can be simultaneously transmitted according to predefined transmission resources over a multi-sector broadcast paging channel reserved for such identical waveforms. Cyclic prefix can be added to the identical waveforms to mitigate problems associated with delay spread and/or time-of-arrival differences at or near sector perimeters. However, this technology addresses only the paging channel, which operates on different transmission channels from the quick page channel and some of the broadcast channels. Thus, problems still exist in the overall paging/management system.